Fix project buffer cycling

* python-django.el:
(python-django-mode-find-next-buffer): Rename from
python-django-mode-find-buffer.
Add settings module to project related buffers

    * python-django.el:
    (python-django-util-shorten-settings): New function.
    (python-django-mgmt-run-command)
    (python-django-open-project): Use it.
Added Static Content Tree View

This is based on a patch by @nHurD, and adds support for both
STATICFILES_DIRS's directory definition formats: string and tuple.
Clean up all byte-compilation warnings

This was done by removing dependency on the cl package macros, namely
`dolist' and `return'.